Earth's far future. Humanity lives in and around an enormous castle-like structure called the Serehfa fastness, a world where the dead can be reborn in digital form and the boundaries between physical and virtual reality have blurred. But a catastrophe called the Encroachment is approaching - a vast dust cloud that will engulf the solar system - and no one knows how to stop it. Four narrators tell the story: a count murdered and forced to spend his remaining digital lives solving his own assassination; a woman who wakes with no memory, pursued by unknown forces; the Chief Scientist searching for a technological solution; and Bascule, a young teller who navigates the data-crypts, narrating in a phonetic dialect that is either maddening or delightful depending on your temperament. Iain M. Banks' most structurally inventive novel.